f150 engine knock
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4wd Low
Joined: May 2024
Posts: 14
Likes: 8
f150 engine knock
so I rebuilt the transmission a couple months ago and had to get surgery on my arm which led to 6 months of recovery meaning the truck sat till now and after I did an oil change and some other basic maintenance I fired it up for the first time since the tranny was installed and it sounded fine but 10 seconds after the engine is running it starts to make a knocking sound first quietly then a bit louder then it kinda stays that way. I was paranoid about the transmission but I think its coming from the valve cover on the passenger side and since it started out fine and slowly gets louder im thinking the oil pressure or something. I have a recording of the sound at idle if anyone is familiar with this sound some advice would be appreciated. it didnt do this at all before I stopped driving it in october.
Fleet Mechanic
Joined: Dec 2003
Posts: 1,436
Likes: 117
From: Virginia
Wow, that is noticeable. 
The video looks like you are on the driver's side, but you mentioned it coming from the passenger's side. Which is it?
A couple of thoughts either way:
1) Most common "knock" sound on the passenger's side is a leaking exhaust manifold / broken studs.
2) Driver's side, on mine the flange of the converter was vibrating on the frame rail fairly loud after I had the exhaust off. (may not be common but happened to me).
Since you had the trans out, you must have dropped the exhaust & it is possible something is not quite back in the optimal location.
It "sounds" like a deeper tone than if it was a failed follower or tensioner / "lifter" that would be directly under the cover.
The video looks like you are on the driver's side, but you mentioned it coming from the passenger's side. Which is it?
A couple of thoughts either way:
1) Most common "knock" sound on the passenger's side is a leaking exhaust manifold / broken studs.
2) Driver's side, on mine the flange of the converter was vibrating on the frame rail fairly loud after I had the exhaust off. (may not be common but happened to me).
Since you had the trans out, you must have dropped the exhaust & it is possible something is not quite back in the optimal location.
It "sounds" like a deeper tone than if it was a failed follower or tensioner / "lifter" that would be directly under the cover.
Thread Starter
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4wd Low
Joined: May 2024
Posts: 14
Likes: 8
sorry it is the drivers side i have a 5 month old baby so my brain doesnt work sometimes. i did have the exhaust out I will have a good look at everything and your comment about it touching the frame may be helpful ill see when i get a chance to look at it the most confusing part is that it takes like 7 seconds and then starts knocking. its silent when it starts. if its the exhaust pressure building up mabe that makes some sense but ill check these things before going down a stupid and expensive rabbithole. thanks.
Fleet Mechanic
Joined: Dec 2003
Posts: 1,436
Likes: 117
From: Virginia
Mine was "similar" in that it took a min or so to start making a racket but that is not due to pressure.
The flange on the driver's side of mine was close enough to the frame rail that once it got some heat into it, it does what metal does with heat.
It expanded just enough & the engine rocking / exhaust pulses knocked on the side of the frame.
I had to loosen everything up & ratchet strap the 2 sides together so they would pull tight towards the center.
Then a chunk of wood to persuade that section away from the rail while I tightened it down.
All quiet after I was done.
The flange on the driver's side of mine was close enough to the frame rail that once it got some heat into it, it does what metal does with heat.
It expanded just enough & the engine rocking / exhaust pulses knocked on the side of the frame.
I had to loosen everything up & ratchet strap the 2 sides together so they would pull tight towards the center.
Then a chunk of wood to persuade that section away from the rail while I tightened it down.
All quiet after I was done.
Thread Starter
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4wd Low
Joined: May 2024
Posts: 14
Likes: 8
today I started it from cold and it was silent for about 15 minutes then slowly started knocking I inspected the exhaust and it isnt tapping against anything but Im thinking that mabe the exhaust manifold could possibly be leaking but it sounds like a lower tone than what I had with that problem on the other side which was dealt with before this. It doesnt seem to be getting any louder and since it took this long to start tapping this time it cant be the engine knocking so ill just insure it and drive it assuming it has something to do with the exhaust and keep an eye on it till I get a chance to take it to a mechanic to see if they can figure it out. stupid sound is like a cricket stick your head in and it jumps to the other side.
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